/*
 * Copyright (c) Kumo Inc. and affiliates.
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <system_error>

#include <melon/shared_mutex.h>

#include <melon/indestructible.h>
#include <melon/lang/exception.h>
#include <melon/portability/sys_resource.h>

namespace melon {
    // Explicitly instantiate SharedMutex here:
    template class SharedMutexImpl<true>;
    template class SharedMutexImpl<false>;

    namespace shared_mutex_detail {
        std::unique_lock<std::mutex> annotationGuard(void *ptr) {
            if (melon::kIsSanitizeThread) {
                // On TSAN builds, we have an array of mutexes and index into them based on
                // the address. If the array is of prime size things will work out okay
                // without a complicated hash function.
                static constexpr std::size_t kNumAnnotationMutexes = 251;
                static Indestructible<std::array<std::mutex, kNumAnnotationMutexes> >
                        kAnnotationMutexes;
                auto index = reinterpret_cast<uintptr_t>(ptr) % kNumAnnotationMutexes;
                return std::unique_lock<std::mutex>((*kAnnotationMutexes)[index]);
            } else {
                return std::unique_lock<std::mutex>();
            }
        }

        uint32_t getMaxDeferredReadersSlow(relaxed_atomic<uint32_t> &cache) {
            uint32_t maxDeferredReaders = std::min(
                static_cast<uint32_t>(
                    melon::nextPowTwo(CacheLocality::system().numCpus) << 1),
                shared_mutex_detail::kMaxDeferredReadersAllocated);
            // maxDeferredReaders must be a power of 2
            assert(!(maxDeferredReaders & (maxDeferredReaders - 1)));
            cache = maxDeferredReaders;
            return maxDeferredReaders;
        }

        long getCurrentThreadInvoluntaryContextSwitchCount() {
#ifdef RUSAGE_THREAD
            struct rusage usage;
            if (getrusage(RUSAGE_THREAD, &usage)) {
                return 0;
            } else {
                return usage.ru_nivcsw;
            }
#else
  return 0;
#endif
        }

        [[noreturn]] void throwOperationNotPermitted() {
            melon::throw_exception<std::system_error>(
                std::make_error_code(std::errc::operation_not_permitted));
        }

        [[noreturn]] void throwDeadlockWouldOccur() {
            melon::throw_exception<std::system_error>(
                std::make_error_code(std::errc::resource_deadlock_would_occur));
        }
    } // namespace shared_mutex_detail
} // namespace melon
